Safe operation of pressurized closed fluid systems requires a careful balance between maintaining the necessary pressure or fluid density to support the application of the system and avoiding exceeding the structural limitations of the system. This balance becomes particularly important when the system is designed for use by average consumers who may not be aware of how to avoid overfilling such a system or understand the risks posed by exceeding the pressure limitations of the system. Examples of such pressurized closed fluid systems include small tanks used to supply pressurized gas to recreational paintball markers and tanks used to store pressurized propane.
The combination of fill and relief valves in a single housing is known. U.S. Pat. No. 3,747,626, the disclosure of which is hereby incorporated by reference as if fully set forth herein, teaches, in part, a combined fill and relief valve wherein the fill valve is biased toward an open position. However, this kind of system does not appear to teach or suggest use as a fill valve where the inlet side is typically left exposed to ambient pressure.
U.S. Pat. No. 6,079,519, the disclosure of which is hereby incorporated by reference as if fully set forth herein, appears to teach, in part, a fill and relief valve with a grease fitting on the inlet side of the valve and a required chamber relief bore disposed between the valve's transverse relief port and the atmosphere in order to vent overpressurized grease to the atmosphere. The apparent resulting additional relief bore length substantially increases susceptibility to clogging of the pressure relieving feature of the valve.
U.S. Pat. No. 5,694,969, the disclosure of which is hereby incorporated by reference as if fully set forth herein, teaches a pressure relief tire valve with independent input and overpressure valves axially aligned with each other. However, the mechanism appears to require the forming or machining of longitudinal grooves along the inner wall of the chamber to allow pressurized fluid to flow around the overpressure valve portion of the mechanism, thereby adding cost and complexity to the manufacturing of the mechanism.
U.S. Pat. No. 7,073,527, the disclosure of which is hereby incorporated by reference as if fully set forth herein, teaches, in part, an apparatus for regulating the internal pressure of a closed system, comprising concentrically aligned intake and release valves. However, as illustrated by the drawings of the disclosure, the mechanism comprises a setting nut which appears to require the tapping of partially hidden threading. Such a machining operation can add significant cost and complexity to the manufacturing of such an apparatus.
Accordingly, there exists a need for a fill and relief valve assembly which is reliable and inexpensive to manufacture, establishes and maintains a fluid seal between the pressurized closed fluid system and the ambient pressure environment when a fill source nozzle is removed from the input side of the valve, and avoids relief port clogging while minimizing the radial diameter of the valve. There is a need for the combination of these features in one valve assembly.